I have some trouble hearing the difference between "ό" and "ω". They kind of sound like the same "o" to me.
Can someone explain this to me? My guess is that "ο" is like a direct, so to say, o-sound and that "ω" is like an oh-sound (if you get what I'm saying). But I'm just guessing here...
The team has posted a lot more on resources in the Greek forums at https://forum.duolingo.com/topic/936 .
If you're on a Microsoft: Go to Settings. Click on Time & Language, then on Language. Find where it says Preferred Languages, then click on Add a preferred language. A menu should pop up with a list of all the languages it has to offer. Find Greek (Ελληνικα) and select it. Click Next, then Install. Wait for it to finish downloading. You should see a small icon on the taskbar that either says ENG or ΕΛ. You can switch between keyboards using Windows key + space. If you're on anything else: Sorry, can't help you.